Summary

Researchers learned some 12 years ago that the AIDS virus, HIV, needs to latch onto a cell protein called CD4 to enter and infect cells. But they've known for a decade that CD4 by itself is not sufficient to get the virus into cells. Also required is some unknown “cofactor.” That cofactor eluded their efforts to discover it, however, until perhaps now. Work reported in this issue indicates that the cofactor is a protein called fusin, a discovery that may help solve several mysteries about AIDS. Among them: how HIV destroys cells and why it appears not to harm some infected people. It may also be possible to limit HIV infectivity by designing new drugs that work by binding to fusin.